Electro-magnetic recording heads



1960 L. NAMENYl-KATZ 2,923,779

ELECTRO-MAGNETIC RECORDING HEADS Filed May '7, 1954 4 Sheets-Sheet 1 lNVEN TOR LIV many!) zZfa/LZ WM Q ATTORNEYS Feb. 2, 1960 L. NAMENYl-KATZ ELECTRO-MAGNETIC RECORDING HEADS 4 Sheets-Sheet 2 Filed May 7, 1954 //V V E N TOR L Katz i .Namgzy i ATTORNEXS Feb. 2, 1960 L. NAMENYIKATZ ELECTRO-MAGNETIC RECORDING HEADS 4 Sheets-Sheet 5 Filed May 7, 1954 IN VENTOR ATTORNEKY Feb. 2, 1960 NAMENYl-KATZ ELECTRO-MAGNETIC RECORDING HEADS 4 Sheets-Sheet 4 V IN VENTOR Filed May 7, 1954 ATTORNEYS United States Patent ELECTRO-MAGNETIC RECORDING HEADS Application Ma 7,1954, Serial No. 428,260

Claims priority, application Great Britain November '2, 1953 2 Claims. (Cl. 179-1002 This invention relates-to 'electro-magnetic recording heads of the kind which are specially designed to record on a continuously moving, magnetically sensitive, tape or wire.

An object of the invention is to provide an electromagnetic head assembly arranged to' provide a highly efficient magnetic circuit in a small physical space, and in a form which is entirely suitable for a number of heads to be mounted close to each other, to record a number of tracks and play back the same, either separately or simultaneously, without causing any appreciable interference between the recordings or reproductions of adjacent tracks.

The invention consists of an electro-magnetic recording head of the kind described in which the electromagnetic element is embraced laterally by, and clamped within, a high electrical conductivity screening member tulghich is in contact with the magnet arms and locates Preferably also high electrical conductivity end plates are provided. The windings of the electro-magnetic element being located in recesses in the magnet arms so that the end plates are in contact with the arms.

By the arrangement described in the preceding two paragraphs a highly effective screening of the magnet is achieved due to. the induced currents which provide a counteracting field and undesirable flux leakages are thereby avoided.

The screening member is preferably arranged to clamp the magnet arms together.

Thus a O-shaped clamping piece may be used of interior profile slightly smaller than, but of the same shape, as the electro-magnetic element and adapted to be clamped around the element by forcing apart the arms thereof. The clamping piece thus holds the ends of the electro-magnetic element together (with a non-ferrous metal strip between to obtainthe required width of magnetic gap).

In order to achieve the accurate location of the poles with respect to each other the magnet arms are preferably hinged together.

The invention further consists of an assembly comprising a plurality of recording heads of the kind described in the previous paragraph secured together with screening plates of high permeability alloy in between adjacent recording heads.

Conveniently a common pivot is provided for the magnetic arms of all the hinged electro-magnetic elements of the assembly.

The invention will be further described with reference to the accompanying drawings.

Figure 1 is an exploded view of a head showing details of the electro-magnetic element and clamp pieces.

Figure 2 is the front elevation of a typical assembly of four heads.

Figure 3 is a cross-section taken through Figure 2.

Figure 4 is a plan view, with the end plates removed, exposing the electro-magnetle element, and. i

, 2,923,779 Patented Feb. 2, 1960 Figure 5 is' a section through the same element.

'Figures 6-9 show modifications.

The laminations 1 and 2 which are made of high permeability magnetic alloy are riveted together in alternate order by rivets 3.

The two ends of the laminations are marked (a) and (b). v

End (a) is formed to provide the pole end of the magnet, while end (b) is shaped and punched with hole (0) to form one part of a hinge. Through this hinge two opposing stacks areheld together by pivot 4 of brass or other non-magnetic alloy.

The two outside layers of the stacks are conveniently cut away as shown to provide recesses for the windings which are formed on both stacks.

The cutting away of the magnetic material or the limbs or arms to allow insertion of the coils does not apparently affect the field at the pole tips and in any event could be compensated for by increasing the width of the limbs at this point. This is preferably not done however because it would increase the length of the wire required for coils, and hence resistance, and this would afiect the bass (low frequency) response.

Clamping piece 5' is made of a high electrical conductivity non-ferrous alloy preferably a hard aluminium or copper alloy. The interior profile is slightly smaller, but of the same shape as the assembled electro-magnetic element.

The two arms of clamping piece 5 may be forced apart to receive the electro-magnetic element having first placed a non-ferrous metal strip 6 between the pole pieces to obtain the required width of magnetic gap.

The assembled head will be held together by the torsion exerted on clamping piece 5.

As Figures 3, 4 and 5 show, a number of assemblies may be sandwiched together separated by screening plates 7 and 8. The screening plates 7 and 8 have the same contour as clamping piece 5. Screening plates 7 are made of high electrical conductivity non-ferrous material such as aluminium or copper and are placed adjacent to each electro-magnetic assembly on both sides, while between the two adjacent plates 7 a plate 8 is placed, which plate 8 is exactly the same size as plate 7 but made of high permeability magnetic alloy of good screening properties. The order of assembly is shown in Figures 2, 3 and 4. Any desired number of recording heads may be so assembled and then held together by clamping screws 9 and may conveniently be fitted with suitably designed terminal boards or connectors.

Various methods of achieving a clamping efiect are possible in addition to the one shown in Figure 1 of'the drawings. Thus a spring 10 may be arranged behind the magnet as shown in Figure 6 or a clamping screw which, however, would be less efficient, and thirdly co-operating projections on the magnet arms and the screening member (see Figure 7).

instead of the hinge to achieve accurate location of the pole tips with'respect to eachother various other modifications are possible, as shown in Figures 8 and 9.

Thus in Figure 8 square recesses are provided in the abutting ends of the magnet arms opposite to the pole tips and these put round a central pin 11.

In Figure 9 the clamping piece 5 is provided with a V-shaped recess and the ends of the magnet arms opposite to the pole tips are shaped to abut and fit into the V- shaped recess.

' I claim:

' 1. An electro-magnetic multiple-track recording head comprising a plurality of magnetic structures stacked in parallel relationship; each structure including two flat magnetic members carrying windings and lying in substantially the same plane, one of the members having an an opening in said extension, end pieces attached to both.

sides of one end of the other member, said end-pieces each being formed with a similar extension directed toward the one member, an opening in said similar extension, the opening in the extension ofthe onev member lying between-the openings of the end pieces of the other member, pole-pieces attached to each member on both sides at its other end, said other end of each member being formed as a pole tip, at least one part of the outer edge of each of said members being formed to a predetermined contour; a layerof non-magnetic material between said pole tips in each of said magnetic structures; a cylindrical member passing through the holes of all said openings to form a common hinge pin by which the two members of each of said magnetic structures are hinged together; a flat C-shaped clamping member. for each of said magnetic, structures made of non-magnetic electrically conductive material, parts of the internal edge of each said clamping member being formed to'contours corresponding with the contours: formed on said outer edges of said members; the elements of each of said magnetic structures being assembled by springing apart the ends of the clamping member and placing the clamping member around the magnetic structure insubstantially the plane of the members with the polestips protruding from said ends and allowing said ends to spring back, whereby the two members. are clamped to- 4',- gether and are simultaneously located with respect to the clamping member and, with respect to, each, other by the interengagement of the edge contours, the clamping member also serving as an electrostatic screen around the major portion of the periphery of the magnetic structure; an end plate of non-magnetic electrically conductive material adjacent each face of each clamping member serving to retain the magnetic structure within its clamping member and also servingas an electrostatic screen; and amagnetic screening member of high permeability material between each pair of adjacent endlplates.

2. A recording head as claimed in claim 1 wherein said windings are laid in recesses formed in the front and rear faces of said. two members of each magnetic structure, whereby said end plates are enabled to make contact with both faces of said members. 1

References Cited in the file of this patent UNITED STATES PATENTS' 2,535,480 Begun Dec. 26, 1950 2,592,652 Buhrendorf Apr. 15, 1952 2,621,259 Grantham Dec. 9, 1952 2,640,886 Davis Jan. 2, 1953 2,658,113 Holmes Nov. 3, 1953 2,749,391 Gumbert. June 5, 1956 2,751,440 De Turk etal. June 19,1956 2,769,036 Selsted ,Oct.' 30, 1956 

